1. Field of the Invention
The invention relates generally to a rearview mirror assembly for a motor vehicle and more particularly to a rearview mirror assembly having a reduced friction power-fold assembly.
2. Description of the Related Art
Motor vehicles typically include at least one external rearview mirror system for providing the operator with a rearward view. The mirror system typically comprises a base attached to the motor vehicle, a reflective element assembly comprising a mirror and a supporting bracket, and an arm assembly interconnecting the reflective element assembly and the base. With large mirrors, such as those found on trucks, the arm assembly will frequently comprise a twin-arm assembly. The reflective element assembly can be adapted for selective unfolding away from, or folding against, the vehicle to position the mirror system in order to minimize the potential for impact when the mirror is not needed, for example when the vehicle is moving through a car wash. This is accomplished by a pivot connection interposed between the base and the arm assembly. The unfolding and folding can be accomplished manually by pushing or pulling the reflective element assembly to pivot the arm assembly relative to the base, or by a remotely controlled, motorized power-fold mechanism incorporated into the pivot connection and adapted for rotation of the arm assembly.
In a motorized power-fold mechanism incorporated into the mirror system, there are advantages to having the mirror system capable of manual folding and unfolding. The operational components (e.g. the motor and transmission assembly) providing the power-fold functionality will typically be resistant to manual movement due to folding and unfolding. There may be occasions when it is desirable to manually fold or unfold the mirror system, such as after the vehicle has been turned off. During operation, or when the vehicle is unattended, such as in a public parking facility, the mirror system can be struck, and forced against the vehicle. This can cause damage to the structural and operational components. Thus, mirror systems with a power-fold assembly will typically incorporate a detent assembly into the pivot assembly.
The detent assembly can comprise opposed contacting bodies which move as a unit under the influence of interconnecting detents during normal power-fold operation, but which will rotate relative to each other in response to impact to or manual movement of the mirror system. The requirement that the pivot assembly be tightly configured in order to minimize undesirable vibration of the mirror system will generally necessitate a significant normal force urging the contacting bodies together. The relative rotation of the contacting bodies can thus involve the development of significant frictional forces as the detents move out of their “at-rest” positions and travel along the opposing contacting body, even though the detent assembly may be fabricated of low-friction materials. These frictional forces can also contribute to wear of the contacting bodies, which will also contribute to vibration and improper operation. Thus, there is a need for a pivot assembly which is coherent and not susceptible to vibration, enables the powered folding and unfolding of the arm assembly relative to the base, and enables the mirror system to be easily manually folded and unfolded.